Apparatus for operating a steam power plant including a reheater and tapped steam operated steam consumers



April 1953 H. VOGLER 3,083,536

APPARATUS FUR OPERATING A STEAM POWER PLANT INCLUDING A REHEATER ANDTAPPED STEAM OPERATED STEAM CONSUMERS Filed Dec. 20, 1960 4 Sheets-Sheet1 Aprll 2, 1963 H. VOGLER 3,083,536

APPARATUS FOR OPERATING A STEAM POWER PLANT INCLUDING A REHEATER ANDTAPPED STEAM OPERATED STEAM CONSUMERS 4 ShetS-ShGt 2 Filed Dec. 20, 1960Apnl 2, 1963 H. VOGLER 3,083,536

APPARATUS FOR OPERATING A STEAM POWER PLANT INCLUDING A REHEATER ANDTAPPED STEAM OPERATED STEAM CONSUMERS Filed Dec. 20, 1960 4 Sheets-Sheet3 F/lg- 6 34 fare/#02":

Aprll 2, 1963 H. VOGLER 3,083,536

APPARATUS FOR OPERATING A STEAM POWER PLANT INCLUDING A REHEATER ANDTAPPED STEAM OPERATED STEAM CONSUMERS Filed Dec. 20, 1960 4 Sheets-Sheet4 INVENTOR. H l/v.5 VSGLEQ.

ATTOP/VEK United States Patent C) Hans Vogler, Winterthur, Switzerland,assignor to Sulzer Freres, S.A., Winter-that, Switzerland, a corporationas Switzerland Filed Dec. 20, 1966, Ser. No. 77,096 Claims priorit,application Switzerland Dec. 26, 1961 r'ilairns. (1. oil-73) The presentinvention relates to a steam power plant including a steam generator, asteam poiwer engine having a high pressure part and a low pressure part,a reheater interposed between said two parts, and an additional steamconsumer whereby steam is selectively tapped from a part of the steampower engine, and/or from the reheater to obtain steam for theadditional consumer.

Steam power plants frequently comprise auxiliary machines, for exampleboiler feed pumps, which are driven by steam turbines. There are alsoother steam consumers, such as heaters, in addition to the main primemover. It is conventional to obtain the steam for operating theauxiliary engines and/ or for satisfying the steam demand of other steamconsumers by tapping steam from the main engine of the plant. Since thepressure of the tapped steam varies according to the load on the mainengine the pressure of the tapped steam is considerably lower when theload on the main engine is low than when this engine operates at fullload. Of course, if the tapped steam operates feed pumps, less energy isrequired for these pumps when the plant operates at low load. However,if the load on the main engine drops below a certain minimum load, thepressure of the tapped steam is insuiiicient to answer the requirementsof the feed pumps and steam must be tapped from a higher stage of themain engine.

It is an object of the present invention to provide in a steam powerplant including a prime mover, such as a turbine, having at least twoexpansion stages and a reheater therebetween and at least one additionalsteam consumer apparatus whereby steam is available for the additionalsteam consumer at a desired pressure and a suitable temperature at allload conditions on the prime mover. According to the invention steam isselectively tapped from the prime mover and/ or from the reheater atrelative rates which depend on the load on the prime mover.

It is a further object of the invention to provide a control apparatusin a plan as specified in the paragraph next above whereby the selectivesteam tapping is automatically effected to efiiciently satisfy the steamrequirements of the additional steam consumer at variable loadconditions on the prime mover and/ or on a steam generator producingsteam for the power plant.

The novel features which are considered characteristic of the inventionare set forth with particularity in the-appended claims. The inventionitself, however, and additional objects and advantages thereof will bestbe understood from the following description of embodiments thereof whenread in connection with the accompanying drawing wherein:

FIG. 1 is a diagram known as a Mollier diagram wherein the abscissaerepresent entropy of steam and the ordinates represent heat content ofsteam and into which the steam conditions in a plant according to theinvention and operating at two different loads are plotted.

FIG. 2 is a digrammatic illustration of a plant according to theinvention.

FIG. 3 is a diagrammaticillustration of a modified portion of the plantshown in FIG. 2.

ansasss Patented Apr. 2, 1963 FIG. 4 is a diagrammatic illustration of amodified plant according to the invention.

FIG. 5 is a diagrammatic part sectional illustration of a controlapparatus for the plant shown in FIG. 4.

FIG. 6 is a diagrammatic illustration of a modification of a part of theplant shown in FIG. 4. 7

FIG. 7 is a diagrammatic part sectional illustration of a controlapparatus for the plant shown in FIG. 6.

FIG. 8 is a diagrammatic illustration of a modified part of theapparatus shown in FIG. 7.

FIG. 1 of the drawing is a diagram wherein the abscissae represententropy of steam and the ordinates represent heat content of steam. Thedotted line shows the steam conditions in a plant operating at full loadand having a steam engine with two expansion stages and a reheatertherebetween. The steam leaving the second stage of the steam engine iscondensed in a condenser. The solid line represents the steam conditionsin the same plant when the plant operates at part load. The isobarending at point A represents the steam conditions within the steamboiler. The steam enters the high pressure part of the steam engine atthe condition A and expands in this high pressure stage to the conditionB. The steam leaving the high pressure part of the steam engine isreheated in the reheater along the isobar B--C. The steam of thecondition C enters the low pressure part of the steam engine wherein thesteam is expanded to the pressure in the condenser. The steam enters thecondenser at the condition D. It is asumed that steam is tapped from thelow pressure part of the steam engine at the condition E. This steam maybe used for operating an auxiliary turbine for driving a pump formingpart of the steam power plant. The adiabatic pressure drop available foroperating the auxiliary turbine is represented by the dotted line EF. Ifthe load on the main steam engine is reduced, the condition of the steamat the outlet of the boiler and at the inlet of the high pressure partof the main engine corresponds to point A; the condition at the outletof the high pressure part and at the inlet of the reheater isrepresented by point the condition of the steam at the outlet of thereheater and at the inlet of the low pressure part is represented bypoint C; the condition of the steam leaving the low pressure part andentering the condenser is represented by point D. The temperature 1 ofthe steam at point A is the same as at point A. If steam is tappedduring part load operation from the low pressure part at the condition Eand at the same tapping point as during full load operation, theavailable adiabatic pressure drop EF' is considerably smaller than thepressure drop E-F available from the tapped steam at full loadoperation. if the pressure drop available from the tapped steam at partload operation is insuflicient for operating the auxiliary turbine,steam of higher pressure must be tapped from the low pressure part ofthe steam engine. If this is done, the temperature of the steam isconsiderably higher and may not be suitable for operating the auxiliaryturbine or satisfying the demand of another steam consumer.

According to the invention, it the pressure drop available from steamtapped at a certain point of a steam engine is insuifi ierrt, tapping isnot switched to a higher pressure oint of the steam engine, but steam istapped from the reheater whereby sufiicient pressure drop can beobtained without raisingthe temperature of the steam entering theauxiliary turbine or consumer.

The condition of the steam tapped according to the invention from thereheater is designated by point G in FIG. 1. This point can be so chosenthat the tapped steam has approximately the same temperature as thesteam of the condition E. The pressure drop available from the steamtapped from the reheater is represented by the line G-H. It has beenfound to be of considerable advantage if auxiliary turbines can :be usedwhich operate at relatively low inlet temperature which temperature doesnot substantially change when the load on the tapped turbine changes.

in the apparatus according to the invention a steam pipe .for conductingsteam from a suitable point of a reheater to an auxiliary machine orother steam consumer is added to the conventional pipe for conductingtapped steam from a main steam engine to the auxiliary steam consumer.Depending on the load on the main steam engine, steam is tapped from thelow pressure stage of the main steam engine or from the reheater; theformer is done when the steam engine operates at full load and thelatter when the steam engine operates at partial load.

A control valve is interposed in at least one of the aforementionedpipes. This valve is preferably controlled according to a workingcondition of the steam plant, for example, the speed of an auxiliaryturbine which is operated by the tapped steam.

In a modified arrangement according to the invention steam is tappedfrom a high pressure stage of the steam engine when the load on theengine is relatively small and is tapped from the reheater when the loadon the main engine is great. It is also within the scope of the presentinvention to selectively tap steam from a high pressure stage of themain steam engine, from the reheater, and from a low pressure stage orthe main steam engine, depending on the load on the latter.

FIG. 2 is a diagrammatic illustration of a steam power plant comprisinga steam generator 1 from which live steam is conducted through a steammain 2 to a high pressure part 3 of a turbine. The steam exhausted fromthe high pressure part is conducted through a pipe 4 to a reheater 5 andtherefrom to a low pressure part 6 of the turbine. The reheater 5includes an intermediate collector '7 from which steam may be conductedthrough a pipe it? to an auxiliary turbine 3 which drives an electricgenerator 9, a valve '11 being interposed in the pipe 1 3. This valve isby-passed by a pipe 12 in which an orifice plate 13 is interposed. Steammay be tapped from the low pressure part 6 of the main turbine andconducted through a pipe 14 containing check valves 15 and 16 to theauxiliary turbine 8. A pipe 17 is connected to the pipe 14 between thecheck valves 15 and '16 for conducting tapped steam to an additionalsteam consumer, for example, a feedwater heater '18. The pressure of thesteam entering the turbine 8 is measured by a conventional device 19.

In order to provide the auxiliary turbine 8 with suitable steam alsoduring periods of low load operation of the turbines 3, 6, the followingcontrol system is pro vided:

At normal load of the main turbine 3, 6 steam is tapped from the lowpressure part 6 and supplied to the turbine 8 through the pipe 14. Thede ice 19 continuously measures the pressure of the steam entering theturbine 8. The steam pressure in the pipe 14 becomes smaller when theload on the turbine 3, 6 is reduced and the pressure-responsive device'19 actuates by means of a conventional control apparatus the valve 11for conducting steam from the reheater 5 to the turbine 8. A certainamount of steam, depending on the size of the orifice in the plate 13,flows through the pipes and 12 also when the valve 11 is closed so thatthe pipe 16 is always heated and condensing of steam therein at a suddenopening of the valve 11 is prevented.

FIG. 3 diagrammatically illustrates a modified control system of theplant shown in FIG. 2. In this case a control valve 20 is provided alsoin the pipe 14. The controlled variable in the control circuit ismeasured by a device 21 which is responsive to the speed of the turbine8. The device 21 actuates the valve 2%} by conventional controlapparatus, which are not shown in detail, opening the valve 29 upon adecrease of the speed of the turbine 8 below the desired speed andclosing the valve 29' upon an increase of the speed of the turbine 8above the desired speed. When the valve 2% is fully open and the speedmeasured by the device 21 is still below the desired speed the valve 11is opened, admitting steam from the reheater 5, opening of the valve 11continuing until the turbine 8 operates at the desired speed. When thevalve 11 is opened the valve 20 is closed and provision of a check valvein the pipe 14 is not absolutely necessary. When the load on the turbine3, 6 is increased to normal or full load whereby the steam generator 1is also operated at full output the pressure of the steam suppliedthrough pipe 1% to the turbine 8 rises, causing an increase of the speedof the turbine and closing of the valve 11 and simultaneously opening ofthe valve 20 so that steam is tapped from the low pressure part 6 of themain turbine for operating the turbine 8.

In the plants schematically illustrated in FIGS. 4 to 6 steam generatedin a boiler 39 having a superheater 3 1 is conducted through a steammain 32 to a high pressure part 33 of a main turbine. The exhaust of thepart 33 is conducted through a pipe 34 into a low pressure part 36 ofthe main turbine, a reheater 35 being interposed in the pipe 34. Steamis tapped from the turbine part 36 through a pipe 37 and conducted to afeedwater preheater 38. Steam is also tapped from the turbine as througha pipe 39 and conducted to a steam consumer 4%. A pipe 4-1 conductssteam tapped from the low pressure turbine 36 to a feedwater preheater42. The exhaust steam of the turbine 36 is conducted through a pipe 43to a condenser 44-. The condensate flows through a pipe 45 to a pump 46which pumps feedwater through the preheater 42 into a feedwater tank 47which supplies feedwater through a pipe as to a feed pump 48 which pumpsthe feedwater through the preheater 38 into the boiler 30. The output ofthe boiler 39 is controlled by conventional means, not shown, tocorrespond to the steam consumption of the turbines 33 and 35, or of thesteam consumers which receive steam from these turbines. The feed pump48 is driven by an auxiliary turbine 56 which receives steam from a pipe52 supplied by steam tapped from an intermediate collector 51 of thereheater S5, or steam which is tapped from the high pressure turbine 33through a pipe 54. A control valve 53 is interposed in the pipe 52 and acontrol valve 55 is interposed in the pipe 54. The valves 53 and 55 arecontrolled by a device 53 which is actuated in response to the steamadmission pressure of the turbine 50 and in response to the speed of theturbine 50 which is measured by a speed-responsive device 56. At normalor full load output of the turbine 33, 36 the valve 53 is opened untilthe turbine 50 operates at the desired speed and the valve 55 is closed.If, upon a decrease of the load on the turbine 33, 3d or of the steamoutput of the boiler 31) the pressure of the steam received by theturbine 50' from the pipe 52 drops and the speed of the turbine 50decreases in spite of full opening of the valve 53, the reduced steamadmission pressure to the turbine 5t acting through the device 53 causesclosing of the valve 53'. At the same time the valve 55 is opened untilthe turbine 50 has the desired speed.

FIG. 5 is a more elaborate illustration of the control system which isdiagrammatically illustrated in FIG. 4.. The device 58 includes acylinder 58; in which a piston 58g reciprocates. The space at the leftside of the piston 58g receives or discharges a pressure fluid through apipe 58a which is connected to a pilot valve 58d controlling flow ofpressure fluid to or from the pipe 58c. The valve 58d is actuated inresponse to the positions of a sleeve 56a of the speed governor 56, themovements of the sleeve 56a being transmitted to the valve 58d by meansof a lever 53b and a connecting rod 580. The piston 58g is connected tothe valves 53 and S5 for simultaneous operation thereof in response tothe position of the piston 58g.

The device operates as follows:

When the main turbine 33, 36 is operated at normal load steam foroperating the auxiliary turbine 56 is tapped from the reheater 35through a pipe 52 in which the valve 53 is interposed. A check valve 80is provided in the pipe 52 between the reheater 35 and the valve 53. Thevalves 53 and 55 are actuated in response to the speed governor 56. Ifthe speed of the pump 48 drops, the connecting rod 580 moves in upwarddirection and operates the valve 58d to admit more pressure fluid intothe space in the cylinder'58f at the left side of the piston 58g,tending to move the piston to the right against the pressure acting onthe right side of the piston which is equal to the pressure of the steamadmitted to the turbine 50 through the pipe 52. Reduction of the speedof the turbine'50 is due to a drop of the steam admission pressure ofthe turbine and the pressure at the left side of the piston 58g isgreater than at the right side so that the piston moves to the right andopens the valve 53, admitting more steam to the turbine 50 and causing arise of the steam admission pressure and of the speed of the turbine.

The valve 55 remains closed until the valve 53 is fully opened. Ifmovement of the piston 58g to the right continues, the valve 53 isclosed and the valve 55 is opened so that steam is supplied to theturbine 50 through the pipe 54 which receives steam from the highpressure turbine 33. This operation prevails when the main turbineoperates at partial load whereby the pressure of the tapped steam isrelatively low. The check valve 89 definitely prevents flow of steamtapped from the turbine 33 through the pipe 54 and the valve 55 into thereheater 35. When the load on the main turbine increases and thepressure in the pipe 54 rises, the increased pressure acts on the rightside of the piston 58 and causes speeding up of the turbine 5t so thatthe pressure on the left side of the piston 58g drops and the piston 58gmoves to the left, opening valve 53 and closing valve 55. 7

FIG. 6 is a diagrammatic illustration of a modified system forcontrolling the steam admission to the auxiliary turbine 50 operatingthe feed pump 48 of a plant as shown in FIG. 4. Numeral -61 designates aconduit for a control signal which corresponds, for example, to the rateof feedwater flow to or the rate of steam flow from the steam generator30. This signal is compared in a conventional device 62 with a signalproduced by the device 56 which is responsive to the speed of theturbine 50 and of the feed pump 48. The signal 17 produced m the device62 corresponds to the desired speed of the feed pump and consequently tothe desired pressure of the steam driving the turbine 59. The signal pis conducted through conduits 63 and 66 to devices 59 and 60 whichcompare the signal p with a signal corresponding to the actual pressureof the steam admitted to the turbine 50 which signal is produced in thedevice 58 which is responsive to the actual pressure of the steamoperating the turbine 50. The devices 59 and 60 control the valves 53and 55, respectively, to admit enough steam to the turbine 50 to producethe desired speed thereof, i.e. to provide the steam admission pressurecorresponding to the signal p The signal p is compared in a conventionaldevice 64 with a signal p produced in a device 65 which is re sponsiveto the pressure of the steam in the intermediate collector 51 of thereheater 35. The signal produced by the device 64 effects selectiveconnection of the devices 59 and 60 to the conduit 66 to permitoperation of the device 60 and the valve 55 as described in theparagraph next above as long as the signal 11 is greater than the signal17 i.e., as long as the required steam admission pressure to the turbine50 is greater than the pressure in the reheater collector 51. If thepressure in the reheater becomes greater than the desired turbineadmission pressure, i.e. if 17 is smaller than p the device 60 isblocked and the valve 55 is closed and the device 59 in the cylinder64a.

6 is permitted to operate for providing the desired turbine admissionpressure by controlling the valve 53.

With the aforedescribed control system the auxiliary turbine 50 isautomatically operated by steam tapped from the reheater when 'the loadon the main turbine 33, 36 is high and is operated by steam tapped fromthe high pressure stage 33 when the load on the turbine is 'low and viceversa.

The control system shown in FIG. 6 is not only applicable to the plantshown in FIG. 4 but can also be applied 'to the plant shown in FIGURES 2and 3 whereby the device 65 would be connected to the pipe 14, and thesignal corresponding to the desired speed of the turbine 8would 'becompared with the signal corresponding to the pressure of the steamtapped from the turbine 6-and the resulting signal would be used forswitching control of the valve 20 to control of valve 11 upon a decreaseof the steam pressure in the pipe 14 below the desired pressure foroperating the turbine 8.

FIG. 7 diagrammatically illustrates a mechanical apparatus forimplementing the system shown in FIG. 6. -As in the apparatus shown inFIG. 5 the sleeve 56a of the governor 56 actuates through a lever 62aand a connecting rod 62b a valve 62c which controls flow of a pressurefluid to or from the conduit 66 and'to and from a control cylinder 64a.A piston-64b is axially movable On the left side of the piston acts thepressure defined by the valve 62c and on the right side of the pistonacts the pressure prevailing in the pipe 52. A three-way valve 64d isconnected to the piston 64b for operation thereby. The valve 64dcontrols flow of signal fluid from the conduit 66 either through aconduit 59a to the left side of a piston 59" in a cylinder 59' orthrough a conduit 60a to the right side of a piston 60 in a cylinder60'. The space at the right side of the piston 59 and the space at theleft side of thepiston 60" are connected by a pipe 58" to the steamadmissionpipe of the turbine 50. The piston 59" actuates the valve 53and the piston 60" actuates the valve 55. Fluid relieve cocks 59b and 6%are connected to the space at the left side of the piston 59" and to thespace at the right side of the piston 66", respectively.

In contradistinction to the apparatus shown in FIG. 5 the fulcrum of thelever 62a is-not stationary, but is displaced in response to a desiredset point for the control system which may correspond, for example, tothe rate of feedwater supplied to the steam generator, or to the rateofoutput of the generator.

The device operates as follows:

The valve 620 is actuated in dependence on the speed of the turbine 50required for effecting the desired rate of feedwater supply to or outputof the steam generator so that the fluid pressure 12 at the left side ofthe piston 64b corresponds to the desired operation of the turbine 50."If the pressure p is greater than the steam pressure p in the pipe 52which receives steam from the re heater 35, the piston 64b moves to theright, placing the valve 64d in the position shown in FIG, 7for-connecting the conduit 66 to the conduit 66a and to the space at theright side of the piston 60" in the cylinder fi'. Depending on thedifference between the pressure p and the steam admission pressure 1 thepiston in the cylinder 60' is moved until the valve 55 is in theposition to admit sufficient steam through the conduit 54 to the turbineto produce the desired turbine speed. The valve 53 is closed because thepressure fluid is relieved by the cock 59b from the left side of thepiston 59", If the pressure p drops below the pressure 11 the piston 64bmoves to the left so that the valve 64d connects the conduit 66 to theconduit 59:; and to the space at the left side of the piston in thecylinder 59', causing operation of the valve 53 which admits steam fromthe reheater to the turbine 50. The device 60 is inoperative at thistime an the pressure is relieved from the right side of the piston 7 60"through the cock 60b and the piston 60" moves to the position forclosing the valve 55.

FIGS. 2 to 7 illustrate examples of the invention whereby steam isselectively tapped from a main turbine or a reheater according to theload on the turbine. FIG. 8 illustrates the adaptation of the systemshown in FIGS. 4 to 7 to the control of the selective tapping of thesteam from the main turbine or from the reheater by a device controllingthe output of the steam generator, for example, as disclosed in PatentNo. 2,962,865. FIG. 8 merely illustrates a detail of the systems shownin FIG. 7 which must be modified in order to make the control directlyresponsive to a steam generator load control device. The latter isdiagrammatically shown in FIG. 8 and designated by numeral 70 andcontrols in the conventional manner, for example the rate of fuelsupply, of

combustion air supply, and of feedwater supply, if desired. The device70 includes a cam 743a acting on a roller 7% connected to a lever 700which actuates the valve 64d shown in FIG. 7. If the valve 64d is in theposition shown in FIG. 8, the conduit 66 is connected to the conduit 59awhen the control device for the steam generator is set for full loadoperation so that the auxiliary turbine 50 receives steam from thereheater through the pipe 52. For operating the steam generator atpartial output the cam 70a is rotated relative to a base 70' to efiectclockwise movement of the valve 64d for connecting the conduit 66 to theconduit 60a so that the turbine 56) is supplied with steam from the highpressure turbine 33 through the pipe 54 and the valve 55. The base 70'of the load control device 70 may be adapted to be swung on the axis ofthe cam 70a, without changing the relative position of the cam and ofthe base, by means of a rod 61' for placing the cam in a positioncorresponding to a desired set point.

I claim:

' 1. A steam plant comprising a steam generator, a steam engine having ahigh pressure stage connected to said generator for receiving steamtherefrom, a reheater connected to said high pressure stage forreceiving the exhaust steam therefrom, said steam engine having a lowpressure stage connected to said reheater for receiving reheated steamtherefrom, a steam consumer using up steam energy, a first steam pipeconnected to said consumer and to one of said stages for directlyconducting steam tapped therefrom to said steam consumer for supplyingsteam energy thereto, a second steam pipe connected to said consumer andto said reheater for tapping steam therefrom and conducting the steamtapped from said reheater to said consumer for supplying steam energythereto, and valve means interposed in each of said pipes forcontrolling the relative flow of steam through said pipes from one ofsaid stages and from said reheater to said consumer.

2. A steam plant as defined in claim 1 wherein said 'valve means in oneof said pipes in a check valve.

3. A steam plant comprising a steam generator, a steam engine having ahigh pressure stage connected to said generator for receiving steamtherefrom, a reheater connected to said high pressure stage forreceiving the exhaust steam therefrom, said steam engine having a lowpressure stage connected to said reheater for receiving reheated steamtherefrom, at least one steam consumer,

a first steam pipe connected to said consumer and to at least one ofsaid stages for conducting steam tapped therefrom to said steamconsumer, a second steam pipe connected to said consumer and tosaidreheater for conducting steam tapped from said reheater to saidconsumer, and flow control means interposed in said pipes for controlling the relative flow of steam through said pipes to said consumer.

4. A steam plant comprising a steam generator, a steam engine having ahigh pressure stage connected to said generator for receiving steamtherefrom, a reheater connected to said high pressure stage forreceiving the exhaust steam therefrom, said steam engine having a lowpressure stage connected to said reheater for receiving reheated steamtherefrom, a steam consumer, a first steam pipe connected to saidconsumer and to one of said stages for conducting steam tapped therefromto said steam consumer, a second steam pipe connected to said consumerand to said reheater for conducting steam tapped from said reheater tosaid consumer, valve means interposed in said pipes for controlling thefiow of steam through said pipes to said consumer, steam pressureresponsive means connected to one of said steam pipes downstream of thevalve means therein and responding to the pressure of the steam enteringthe consumer, and actuating means connected to at least one of saidvalve means and connected to said pressure responsive means foractuating said valve means to increase steam admission to said consumerwhen said steam pressure drops below a predetermined pressure and todecrease steam flow to said consumer when said steam pressure exceeds apredetermined pressure.

5. A steam plant comprising a steam generator, a steam engine having ahigh pressure stage connected to said generator for receiving steamtherefrom, a reheater connected to said high pressure stage forreceiving the exhaust steam therefrom, said steam engine having a lowpressure stage connected to said reheater for receiving reheated steamtherefrom, an auxiliary steam engine, a first steam pipe connected tosaid auxiliary steam engine and to one of said stages for conductingsteam tapped therefrom to said auxiliary steam engine, a second steampipe connected to said auxiliary steam engine and to said reheater forconducting steam tapped from said reheater to said auxiliary steamengine, valve means interposed in said pipes for controlling the flow ofsteam through said pipes to said auxiliary steam engine, engine speedresponsive means connected to said auxiliary steam engine, and actuatingmeans connected to at least one of said valve means and to said speedresponsive means for actuating said valve means to increase steam flowto said auxiliary engine when the engine speed drops below apredetermined speed and to decrease steam flow to said auxiliary engineupon an increase of the engine speed above a predetermined speed.

References Cited in the file of this patent UNITED STATES PATENTS

1. A STEAM PLANT COMPRISING A STEAM GENERATOR, A STEAM ENGINE HAVING AHIGH PRESSURE STAGE CONNECTED TO SAID GENERATOR FOR RECEIVING STEAMTHEREFROM, A REHEATER CONNECTED TO SAID HIGH PRESSURE STAGE FORRECEIVING THE EXHAUST STEAM THEREFROM, SAID STEAM ENGINE HAVING A LOWPRESSURE STAGE CONNECTED TO SAID REHEATER FOR RECEIVING REHEATED STEAMTHEREFROM, A STEAM CONSUMER USING UP STEAM ENERGY, A FIRST STEAM PIPECONNECTED TO SAID CONSUMER AND TO ONE OF SAID STAGES FOR DIRECTLYCONDUCTING STEAM TAPPED THEREFROM TO SAID STEAM CONSUMER FOR SUPPLYINGSTEAM ENERGY THERETO, A SECOND STEAM PIPE CONNECTED TO SAID CONSUMER ANDTO SAID REHEATER FOR TAPPING STEAM THEREFROM AND CONDUCTING THE STEAMTAPPED FROM SAID REHEATER TO SAID CONSUMER FOR SUPPLYING STEAM ENERGYTHERETO, AND VALVE MEANS INTERPOSED IN EACH OF SAID PIPES FORCONTROLLING THE RELATIVE FLOW OF STEAM THROUGH SAID PIPES FROM ONE OFSAID STAGES AND FROM SAID REHEATER TO SAID CONSUMER.